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Abstract

In light of the heavy reliance of the people of the Niagara Peninsula on the T\\'elve
Mile Creek (TMC) watershed for recreational activities and for municipal and industrial uses
( e.g., drinking water, shipping and discharge of effluents), it was deemed prudent to assess
the envirol1tnental health of the system by analysing the sediments total and exchangeable
metal, and TPH contents. The MOEE has set guidelines with limits for the protection and
management of aquatic sediments, and the sediments from the headwaters of the TMC have
total metal and TPH (subset of O&G) contents well below the lower provincial limits. Areas
of environmental concern where total metal contents in sediments, either individually or
collectively, exceed the guideline, are the south side of Lake Gibson, the Old WeIland Canal,
a segment of TMC just south of the QEW and Martindale Pond. The total metal content of
sediments does not in all instances identify areas of biological concern. Instead, it has been
found that the exchangeable metal fraction of sediments is a better indicator of metal
availability and thus potential accumulation in organisms. In some instances, the exchangeable
metal fraction agrees with the total metal fraction defining areas of environmental concern,
but it does vary from site to site reflecting the natural variability of the ambient environment.
Overall, the exchangeable metal fraction of sediments appears to be a better indicator of
anthropogenic pollution and ecosystem impact.
A histochemical study of Anodon.ta sp., Elliptio sp. and zebra mussels (Dreissena
polyn'101pha) was done in conjunction with passive biomonitoring of zebra and quagga
mussels (Dreissena bugensis) from the Twelve Mile Creek watershed and Lake 51. Clair
(Jeanette's Creek, Chatham, Ontario). The highest concentrations of divalent metals such as
Cu, Ni, Cd, and Zn, and trivalent Al appear to accumulate in gill and kidney tissues. Metal
contents of organ tissues in Anodonta sp. vary with size class. Organ metal content varies
among size classes, thus requiring consideration of size in biomonitoring studies. Shucked
zebra and quagga mussel tissues, exhibited similar size class to Al content trends. In addition
they reflected the Al content trends of top (approximately 10 cm) most sediments in the
Twelve Mile Creek watershed. Quagga mussels appear to have higher Al concentrations than
zebra mussels, thus suggesting that quagga mussels may be better passive biomonitors of AI.
Cd content in zebra mussel tissues, seemed to increase with size class trends. This was not
demonstrated in the quagga mussel tissues. This suggests that Cd may be regulated by quagga
mussels and not by zebra mussels, and that zebra mussels may be better passivebiomonitors
of Cd than are quagga mussels.
Zebra mussel, quagga mussel, Anodonta sp., and Elliptio sp. were used in a two part,
active (translocated) biomonitoring study of the Twelve Mile Creek watershed. There was no
statistical difference in death rates between zebra and quagga mussels after 65 days of
biomonitoring. However there does appear to be a difference of death rates between sites.
Unfortunately the data base did not permit us to differentiate between sites. Relative to Port
Colborne Harbour (Port Colborne, Ontario), the Twelve Mile Creek watershed appears to be
elevated in bioavailable AI. An area near the terminus of the Twelve Mile Creek appears to
be an area of environmental concern since mussels seemed to have accumulated relatively
large concentrations of Cd, Zn, and Pb. In addition to possible metal loading from a nearby
outfalls, or possible upstream outfalls, road salt runoff from storm sewers may have
contributed to metal accumulation through cation exchanges processes. Similar trends in
cumulative quagga mussel metal concentrations during the two time periods (65 and 159
days), suggest that quagga mussels may reach equilibrium within 65 days of translocation.
Differences in bioaccumulated metal concentrations of the two dreissenid species demonstrate
that active biomonitoring studies must use a variety of organisms to adequately assess the
environmental situation of specific waterways and/or bodies.